September 2007 - Boost-users

Re: [Boost-users] Question about pool.
by 蹬三轮的 25 Sep '07

25 Sep '07

> We use boost pool in our project and we found boost's pool may occupy > too much memory. Say, if we need a block of memory which size is > 1317B, boost's pool will allocate a truck of memory 5268B on a 32bits > platform, leave 3951 bytes unused (it get worse on 64bits platform). I > don't think it is necessary to allocate 5268B, for the sake of > performance, only 1320B is enough for align. It should be resovled > because pool is so important to many large application. pool allocates several blocks of memory at once, then divvies them out. Nothing is wasted. Or did you have something else in mind? -- Cory Nelson Hi Nelson, thanks for your reply. According to the description of pool, it should be working like you said. But actually it is not the same. Hereby, there are two cases provided. I think you will find two totally different results between them. 1. blocksize = 1316 Everything is ok. . 2. blocksize =1317 Disaster! You can notice the waste allocated memory. I just want case 2 to run like case 1. Following is the code, you can check it. 1. i: 0 need: 41(KB) alloc: 41(KB) waste: 8(B) i: 32 need: 82(KB) alloc: 82(KB) waste: 8(B) i: 96 need: 164(KB) alloc: 164(KB) waste: 8(B) i: 224 need: 329(KB) alloc: 329(KB) waste: 8(B) i: 480 need: 658(KB) alloc: 658(KB) waste: 8(B) i: 992 need: 1(MB) alloc: 1(MB) waste: 8(B) i:2016 need: 2(MB) alloc: 2(MB) waste: 8(B) i:4064 need: 5(MB) alloc: 5(MB) waste: 8(B) i:8160 need: 10(MB) alloc: 10(MB) waste: 8(B) 2. i: 0 need: 41(KB) alloc: 164(KB) waste: 123(KB) i: 32 need: 82(KB) alloc: 329(KB) waste: 246(KB) i: 96 need: 164(KB) alloc: 658(KB) waste: 493(KB) i: 224 need: 329(KB) alloc: 1(MB) waste: 987(KB) i: 480 need: 658(KB) alloc: 2(MB) waste: 1(MB) i: 992 need: 1(MB) alloc: 5(MB) waste: 3(MB) i:2016 need: 2(MB) alloc: 10(MB) waste: 7(MB) i:4064 need: 5(MB) alloc: 20(MB) waste: 15(MB) i:8160 need: 10(MB) alloc: 41(MB) waste: 30(MB) here is the sample code: #include <iostream> #include <boost/pool/pool.hpp> #include <iomanip> #include <boost/lexical_cast.hpp> using namespace std; int i = 0; int nextSize = 0; int blockSize = 1317; string sizeFormat(int n) { if (n < 1024) { return boost::lexical_cast <string> (n) + "(B)"; } else if (n < 1048576) { return boost::lexical_cast <string> (n / 1024) + "(KB)"; } else { return boost::lexical_cast <string> (n / 1048576) + "(MB)"; } } struct MyAllocator { typedef std::size_t size_type; typedef std::ptrdiff_t difference_type; static char * malloc(const size_type bytes) { int need = nextSize * blockSize; int waste = bytes - need; cout << "i:" << setw(4) << i << " need:" << setw(10) << sizeFormat(nextSize * blockSize) << " alloc:" << setw(10) << sizeFormat(bytes) << " waste:" << setw(10) << sizeFormat(waste) << endl; return new (std::nothrow) char[bytes]; } static void free(char * const block) { delete [] block; } }; int main() { //typedef std::vector <int, MA <int> > MYVector; boost::pool <MyAllocator> intPool(blockSize); for (i = 0; i < 10000; ++i) { nextSize = intPool.get_next_size(); intPool.malloc(); } }

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problem with boost::any, boost::lambda
by Fei Liu 25 Sep '07

25 Sep '07

The following small code snippet does not compile with boost 1.33.1. What did I do wrong or the library is limited in what it can do? g++ -fstrict-aliasing -fomit-frame-pointer -Wall -pedantic -ansi -g -O2 anytest.cpp -o anytest anytest.cpp: In function ‘int main()’: anytest.cpp:22: error: ‘const struct boost::lambda::lambda_functor<boost::lambda::placeholder<1> >’ has no member named ‘type’ gcc version 4.1.1 20060525 (Red Hat 4.1.1-1) #include <iostream> #include <string> #include <vector> #include <algorithm> #include <boost/any.hpp> #include <boost/lambda/lambda.hpp> #include <boost/lambda/if.hpp> using namespace std; using namespace boost::lambda; using namespace boost; using boost::any_cast; int main(){ vector<any> a; any val = 3; a.push_back(val); val = string("456"); a.push_back(val); std::for_each(a.begin, a.end(), if_then(_1.type() == typeid(int))[cout << _1 << ' ']); }

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boost lambda document example does not compile
by Fei Liu 25 Sep '07

25 Sep '07

Hello, group I am trying out the code snippet in http://www.boost.org/doc/html/lambda/le_in_details.html 'Naming delayed constants and variables'. I got some compile errors complaining about synthesized method error with the following code: #include <iostream> #include <boost/lambda/lambda.hpp> #include <boost/ref.hpp> #include <vector> #include <iterator> #include <algorithm> using namespace std; using namespace boost::lambda; using namespace boost; int main(){ int i = 1; (_1 += 2)(i); // i is now 3 (++_1, cout << _1 << '\n')(i); // i is now 4, outputs 4 int j = 40; _1 = j; var(i) = _1 = j; cout << i << '\n'; vector<int> a; a.reserve(10); a.resize(10); //for_each(a.begin(), a.end(), istream_iterator<int>(cin)); // for_each(a.begin(), a.end(), cin >> _1); i = 0; for_each(a.begin(), a.end(), (_1 = var(i)++)); // delayed evaluation through 'var' for_each(a.begin(), a.end(), cout << _1 << ' '); cout << '\n'; for_each(a.begin(), a.end(), cout << ' ' << _1); cout << '\n'; for_each(a.begin(), a.end(), (var(j) = _1, _1 = var(i), var(i) = var(j))); //<------------ Error for_each(a.begin(), a.end(), cout << _1 << ' '); cout << '\n'; }

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[multi_index] modify problem with composite_key
by Jeffrey Holle 24 Sep '07

24 Sep '07

I am having problems using the modify method with my composite_key. Here is my multi_index container definition: typedef multi_index_container< entry, indexed_by< ordered_unique<member<entry,DataVertex,&entry::m_vertex> >, ordered_non_unique< composite_key< entry, member<entry,int,&entry::m_y>, member<entry,int,&entry::m_x> > > > > C; C m_c; namespace ll=boost::lambda; typedef nth_index<C,1>::type XYINDEX; I have a XYINDEX::iterator that is defined using the equal_range method of an XYINDEX order. Now I wish to modify the m_x attribute that this iterator points to so I attempt to write: inline void Positioner::updateX(XYIterator iter,int x) { m_c.modify(iter,(&ll::_1)->*&Positioner::entry::m_x=x); } I get this compiler error: positioner.h:77: error: no matching function for call to 'boost::multi_index::multi_index_container<Positioner::entry, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::member<Positioner::entry, unsigned int, &Positioner::entry::m_vertex>, mpl_::na, mpl_::na>, boost::multi_index::ordered_non_unique<boost::multi_index::composite_key<Positioner::entry, boost::multi_index::member<Positioner::entry, int, &Positioner::entry::m_y>, boost::multi_index::member<Positioner::entry, int, &Positioner::entry::m_x>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, mpl_::na, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<Positioner::entry> >::modify(boost::multi_index::detail::bidir_node_iterator<boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::index_node_base<Positioner::entry> >, mpl_::na>&, const boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::assignment_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::action<2, boost::lambda::other_action<boost::lambda::member_pointer_action> >, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::addressof_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >, int Positioner::entry::* const, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >, const int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >)' I have also tried: m_c.modify_key(iter,ll::_1=x); But this gives me this error: positioner.h:78: error: no matching function for call to 'boost::multi_index::multi_index_container<Positioner::entry, boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::member<Positioner::entry, unsigned int, &Positioner::entry::m_vertex>, mpl_::na, mpl_::na>, boost::multi_index::ordered_non_unique<boost::multi_index::composite_key<Positioner::entry, boost::multi_index::member<Positioner::entry, int, &Positioner::entry::m_y>, boost::multi_index::member<Positioner::entry, int, &Positioner::entry::m_x>, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, mpl_::na, mpl_::na>, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na, mpl_::na>, std::allocator<Positioner::entry> >::modify_key(boost::multi_index::detail::bidir_node_iterator<boost::multi_index::detail::ordered_index_node<boost::multi_index::detail::index_node_base<Positioner::entry> >, mpl_::na>&, const boost::lambda::lambda_functor<boost::lambda::lambda_functor_base<boost::lambda::other_action<boost::lambda::assignment_action>, boost::tuples::tuple<boost::lambda::lambda_functor<boost::lambda::placeholder<1> >, const int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > >)' While a method like this compiles and works, I would like to be more efficent: inline void Positioner::updateX(DataVertex vertex,int x) { C::iterator iter=m_c.find(vertex); assert(iter!=m_c.end()); m_c.modify(iter,(&ll::_1)->*&Positioner::entry::m_x=x); } Can somebody tell me if what I'm trying to do is possible? If so, how?

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[continued][boost::fusion v2 and xpressive] versioning conflicts...
by Ovanes Markarian 24 Sep '07

24 Sep '07

Eric, sorry for the delay. I only now found some time to work on that issue: http://lists.boost.org/boost-users/2007/08/30120.php After analysing your post and investigation what's going on, I would like to write my opinion: changing xpressive_fwd.hpp or proto_fwd.will not help. I grepped where fusion includes are used and need to enclose these in some conditional statements: #ifdef BOOST_XPRESSIVE_FUSION_V2 # include ... //fusion 2 headers #else # include ... // fusion 1 headers #endif Actually this can be done using some kind of a macro function like: #include BOOST_XPRESSIVE_FUSION_ROOT(sequence/cons.hpp) ... The macro function will deliver the root dependent on the predefined macros like: 1. if !defined XPRESSIVE_FUSION_ROOT and use V2 => choose the root for V2 else => choose the root for V1 As I found out the following files need to be changed: linker.hpp alternate_matcher.hpp alt_compilers.hpp any.hpp cons.hpp arg_traits.hpp op_base.hpp proto_fwd.hpp If you give me your green light I will do it and submit a patch. With Kind Regards, Ovanes

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boost lambda document example does not compile
by Fei Liu 24 Sep '07

24 Sep '07

Hello, group I am trying out the code snippet in http://www.boost.org/doc/html/lambda/le_in_details.html 'Naming delayed constants and variables'. I got some compile errors complaining about synthesized method error with the following code: #include <iostream> #include <boost/lambda/lambda.hpp> #include <boost/ref.hpp> #include <vector> #include <iterator> #include <algorithm> using namespace std; using namespace boost::lambda; using namespace boost; int main(){ int i = 1; (_1 += 2)(i); // i is now 3 (++_1, cout << _1 << '\n')(i); // i is now 4, outputs 4 int j = 40; _1 = j; var(i) = _1 = j; cout << i << '\n'; vector<int> a; a.reserve(10); a.resize(10); //for_each(a.begin(), a.end(), istream_iterator<int>(cin)); // for_each(a.begin(), a.end(), cin >> _1); i = 0; for_each(a.begin(), a.end(), (_1 = var(i)++)); // delayed evaluation through 'var' for_each(a.begin(), a.end(), cout << _1 << ' '); cout << '\n'; for_each(a.begin(), a.end(), cout << ' ' << _1); cout << '\n'; for_each(a.begin(), a.end(), (var(j) = _1, _1 = var(i), var(i) = var(j))); <------------ Error for_each(a.begin(), a.end(), cout << _1 << ' '); cout << '\n'; }

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[ptr_container] Does ptr_map delete objects if inserting fails?
by Boris 24 Sep '07

24 Sep '07

struct foo { }; boost::ptr_map<int, foo> bar; bar.insert(1, new foo()); bar.insert(1, new foo()); Does this code leak? Or does bar delete the second instance of foo? Boris

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Thread, communicate data from main program to thread(s) and back
by Torsten Mohr 24 Sep '07

24 Sep '07

Hi, i've set up an example of a main program that starts two threads and then sends some data to those thread(s). When the thread(s) have processed the data they should notify the main program/thread and wait for new data. I'd like to make sure that what i write is also portable and does not just by chance work on the platform i use. boost::condition seems to be the right thing to look at, is that right? Is there some example for data communication between threads available? Best regards, Torsten.

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[ptr_container] Why is the key passed to ptr_map by non-const reference?
by Boris 24 Sep '07

24 Sep '07

Before anyone refers me to the FAQ at http://www.boost.org/libs/ptr_container/doc/faq.html#why-does-ptr-map-t-ins… - I read it. While it's clear why a reference is used I don't understand why it is a *non-const* reference. Any reason why it's not const? Boris

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scheming with spirit
by jono 23 Sep '07

23 Sep '07

hello all, i'm building a scheme interpreter with spirit and boost. it needs to be simple and robust enuf for a demanding production environment. i've looked for evidence of somebody else having built a scheme or lisp with spirit and boost, and have been surprised to find nothing. it seems like something that almost falls out of the existing classes (variant, shared_ptr, spirit..). it amazes me how few people understand the simplicity of power of lisp and the interpreter pattern in general. the first paper on lisp was published in 1958, and you only have to look at xml to see how relevant list processing is today. an optimal lisp implementation built with spirit & boost could be extremely concise and elegant, but i'm pretty new to spirit and i'm not sure i have the time to find it. my efforts so far are pure kludgery. i think a lisp interpreter included in the boost example code, or even a full boost class, would be very useful. with traits specialization it could be very flexible, and it would introduce an interesting tool for prototyping and testing other boostified code. does anybody know of an existing spirit/lisp implimentation, and is there any interest in developing such a project in open source? cheers jono poff Day One Digital Media Ltd. Auckland, NZ

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